This invention relates generally to gas turbines, engines and more particularly to an apparatus for heating the hub of a frame of a gas turbine engine.
A gas turbine engine includes a compressor that provides pressurized air to a combustor wherein the air is mixed with fuel and ignited for generating hot combustion gases. These gases flow downstream to one or more turbines that extract energy therefrom to power the compressor and provide useful work such as powering an aircraft in flight. In a turbofan engine, which typically includes a fan placed at the front of the core engine, a high pressure turbine powers the compressor of the core engine. A low pressure turbine is disposed downstream from the high pressure turbine for powering the fan.
The rotating components of a gas turbine engine are supported by bearings mounted in one or more structural frames. The frames typically take the form of an inner hub connected to a outer casing by an array of radially extending airfoil-shaped struts. Typical turbofan engines have a fan frame just aft of the fan rotor and a turbine rear frame aft of the low pressure turbine. Turbine rear frames share a common problem in the presence of hub-to-case transient and steady-state thermal gradients which can develop because the hub region is typically more massive than the casing, coupled with the fact that the case is typically 100% exposed to the hot flowpath gases while only one of 3 or 4 hub walls is similarly exposed. This results in a much more rapid transient response of the casing relative to the hub, resulting in potentially destructive thermal stresses in the turbine frame. It is known to alleviate these stresses by heating the hub of a turbine frame, therefore reducing the thermal gradients. However, known systems for heating turbine frame hubs typically require modification to the turbine frame and the addition of extra components, which increases the cost and complexity of the turbine frame design.
Accordingly, there is a need for a simple and economical method of heating turbine frame hubs.
The above-mentioned need is met by the present invention, which in one aspect provides a frame for a gas turbine engine comprising a central hub having a circumferentially extending flowpath surface enclosing an interior cavity and an annular outer casing connected to the hub by a plurality of struts extending radially from the hub to the casing, wherein the flowpath surface has a plurality of inlets disposed in the in flow communication with the interior cavity and a plurality of outlets disposed in flow communication with the interior cavity. In another aspect, the invention provides a flowpath member for a turbine frame hub having a plurality of inlets and outlets formed therein.
The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.